INDUSTRIAL APPLICABILITY. The present invention finds applicability in the transportation industries, and more specifically in land based motor vehicles such as automobiles and trucks. Of particular importance is the invention""s utility in the frame arrangements of passenger vehicles.
Presently, motor vehicles are built around a frame structure that includes a system of interconnected frame members upon which passenger compartments are carried. Lower portions of such frames having primary members that run substantially longitudinally under the vehicle and which are commonly known as rails. These rails, of which there are normally two, are typically configured to include at least two changes in elevation between the front and back of the vehicle. These elevational changes are facilitated by bends in the rails"" length. Such bends may be required to accommodate such structural features as axles and other parts of the vehicle that are located in close proximity to the rails, or are located where the rails would extend if not bent. Another general occurrence in the rails"" configuration is a bend down behind the engine compartment to a lower elevation below the passenger compartment. A similar configuration is often affected at the back of the vehicle as well with the rails bending up from under the passenger compartment to a higher elevation below the trunk compartment.
During a head-on or rear-end collision, the rails experience bending moments at these bends. Depending on the severity of the collision, failure of one or both of the rails can occur at the bends. This is particularly worrisome because these bends are often located in close proximity to the operator and/or other occupants in the passenger compartment. This is especially true with respect to the front bends that turn down from an elevation under the engine compartment to a lower elevation under the front portion of the passenger compartment. In this configuration, the front bends of each of the two rails are extremely close to the foot well(s) of the front seat occupants. If one or both of the rails fail at their front bends, for instance in a head-on collision, the resulting change to the rails at the bends can cause them to project into the passenger compartment causing injury to the occupants. Still further, a rail failure can result in other components of the vehicle being allowed to be pushed into the passenger compartment. A prime example is again, a head-on collision that causes a frame failure at the front bend. Because of the lost integrity of the frame, components from the engine compartment may be allowed to be pushed back into the passenger compartment with grave results to the occupants.
To eliminate, or at least reduce such rail failures, vehicle designers are known to engineer the distal portions (those portions of the rail close in proximity to the ends of the rail) of the rails to give-way before the interior portion of the rails. In this manner, energy from a collision is dissipated by the collapse of the rail structure itself, primarily at the specially designed distal end(s). Obviously, the strength of the interior or support portion of the rail controls an upper strength limit of the yieldable distal portions of a rail. That is to say, the distal ends must always be xe2x80x9csofterxe2x80x9d than the middle portions of the rail, or the rail will not fail as designed, which is first at the end portions.
A limiting design parameter is usually the bend feature since this area is most susceptible to failure due to the bending moments that are caused in this area of the rail. It is easy to appreciate that without the vulnerable bend(s), the distal portions of the rails would be able to be strategically strengthened to dissipate greater amounts of crash energy during their controlled collapse.
The easiest remedial approach that enables an increase in distal rail strength, and one that has been exploited by others, is to eliminate or reduce the severity of the bends in the rails. This, however, generally results in a significant reduction in the passenger compartment size and can even affect the vehicle""s performance and handling characteristics.
Another way in which vehicle designers have enabled increases in distal end rail strength is by reinforcing the portions of the rails adjacent to the bend areas with extra plates or other such strengthening-type members. Similarly, increases to the dimensions of the rails, such as their thickness, have also been tried for such strengthening purposes. These types of strengthening measures, because of the associated increase in bulk, are difficult to affect in confined spaces, such as in the vicinity of an engine compartment, firewall, foot well and drive shaft tunnel areas. To accommodate such reinforcements, the floor of the passenger compartment has normally been required to be raised higher off the ground, and/or walls of the passenger compartment are recessed inwardly into the compartment. Detrimentally, both remedies result in reduced passenger compartment size. Further, by raising the floor of the passenger compartment, the vehicle""s handling characteristics and performance are diminished. That is to say, by raising the passenger compartment, the vehicle""s profile and center of gravity are consequently raised. Elevating the vehicle""s profile increases wind resistance compromising fuel economy and handling characteristics, while elevating the vehicle""s center of gravity also causes handling problems and increases the vehicle""s tendency for roll-over accidents.
Reinforcement by increasing the dimensions of the rails in the vicinity of the bends is also not an optimal solution; such reinforcement typically results in an undesirable weight increase that adversely effects the performance of the vehicle and increases the complexity of manufacturing the vehicle frame. Until the present invention, vehicle frame designers have been forced to compromise performance and passenger compartment capacity, as well as detrimentally increase the weight of the vehicle in order to achieve stronger frames and enable more crash absorbent rail members.
In view of the above described deficiencies associated with known rail strengthening measures, the present invention has been developed to alleviate these drawbacks and provide additional benefits in at least safety and performance. These enhancements and benefits are described in greater detail hereinbelow with respect to alternative embodiments of the present invention.
In the disclosed embodiment(s), the present invention alleviates the drawbacks described above with respect to known vehicle frames and incorporates several additionally beneficial features. The invention eliminates, or at least significantly reduces, the bending moments experienced at the bends of a rail. This is accomplished by incorporating a force or load distributing arrangement that includes three support members (two members besides the portion of the rail that achieves the change in elevation) positioned substantially at the bend that distributes impact loads experienced at the distal end of the rail as axially loads to the support members. Furthermore, the support configuration makes the load transfer substantially without bending moments being induced in any of the support members. This arrangement allows greater distal rail strength for dissipating crash forces without compromising passenger compartment size or handling and performance characteristics of the vehicle. Moreover, this arrangement is a scalable structure which does not require extensive design modifications as the frame dimensions are increased or decreased to accommodate larger and smaller vehicle platforms. Still further, the support configuration of the invention provides a stronger overall frame structure that results in a quieter vehicle, as well as a vehicle that handles better because of its more rigid or xe2x80x9ctightxe2x80x9d frame. This strengthening of the frame, as well as the unique configuration of the support members of the new arrangement, better protects occupants inside the passenger compartment because it is harder to compromise. Additionally, the arrangement of the support members forms a xe2x80x9cprotective cagexe2x80x9d about the front seat passenger foot well further protecting the passenger compartment from intrusions by other components of the vehicle under crash circumstances. Of particular significance is the characteristic of the support members"" design that helps to establish a barrier between the feet of the front seat passengers and the front wheel assemblies of the vehicles. Heretofore, it was not uncommon for the front wheel assemblies to be pushed back into the foot well area causing injury to the passengers"" feet and legs in head-on collisions.
The general beneficial effects described above apply generally to each of the exemplary descriptions and characterizations of the frame designs disclosed herein. The specific structures through which these benefits are delivered will be described in detail hereinbelow.